+ mm-vmalloc-extend-page-table-walk-to-support-larger-page_shift-sizes-and-eliminate-page-table-rewalk.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/vmalloc: extend page table walk to support larger page_shift sizes and eliminate page table rewalk
has been added to the -mm mm-new branch.  Its filename is
     mm-vmalloc-extend-page-table-walk-to-support-larger-page_shift-sizes-and-eliminate-page-table-rewalk.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmalloc-extend-page-table-walk-to-support-larger-page_shift-sizes-and-eliminate-page-table-rewalk.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: "Barry Song (Xiaomi)" <baohua@kernel.org>
Subject: mm/vmalloc: extend page table walk to support larger page_shift sizes and eliminate page table rewalk
Date: Sat, 07 Nov 2026 21:49:50 +0800

vmap_pages_range_noflush_walk() (formerly vmap_small_pages_range_noflush())
provides a clean interface by taking struct page **pages and mapping them
via direct PTE iteration. This avoids the page table rewalk seen when
using vmap_range_noflush() for page_shift values other than PAGE_SHIFT.

Extend it to support larger page_shift values, and add PMD- and
contiguous-PTE mappings as well.

Rename it to vmap_pages_range_noflush_walk() since it now handles
more than just small pages.

For vmalloc() allocations with VM_ALLOW_HUGE_VMAP, we no longer need to
iterate over pages one by one via vmap_range_noflush(), which would
otherwise lead to page table rewalk. The code is now unified with the
PAGE_SHIFT case by simply calling vmap_pages_range_noflush_walk().

The pages array may hold several physically discontiguous chunks that
are mapped with the same @shift. If the virtual range is not aligned to
the chunk size, a PMD boundary can split a chunk, and the walk resumes
in the next PMD in the middle of it. arch_vmap_pte_range_map_size()
only checks CONT_PTE_SIZE alignment there and could map past the end of
the chunk, so clamp each PTE-level mapping to the remainder of the
current chunk.

Link: https://lore.kernel.org/20261107134953.748622-8-jiangwenxiaomi@gmail.com
Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
Signed-off-by: Wen Jiang <jiangwen6@xiaomi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Xueyuan Chen <xueyuan.chen21@gmail.com>
Tested-by: Leo Yan <leo.yan@arm.com>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Christophe Leroy <chleroy@kernel.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Andrew Donnellan <andrew+kernel@donnellan.id.au>
Cc: Wen Jiang <jiangwenxiaomi@gmail.com>
---

 mm/vmalloc.c |   88 ++++++++++++++++++++++++++++++-------------------
 1 file changed, 54 insertions(+), 34 deletions(-)

--- a/mm/vmalloc.c~mm-vmalloc-extend-page-table-walk-to-support-larger-page_shift-sizes-and-eliminate-page-table-rewalk
+++ a/mm/vmalloc.c
@@ -558,8 +558,11 @@ void vunmap_range(unsigned long addr, un
 
 static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr,
 		unsigned long end, pgprot_t prot, struct page **pages, int *nr,
-		pgtbl_mod_mask *mask)
+		pgtbl_mod_mask *mask, unsigned int shift)
 {
+	const unsigned long chunk_pages = 1UL << (shift - PAGE_SHIFT);
+	unsigned long pfn, size, chunk_end;
+	unsigned int nr_pages;
 	int err = 0;
 	pte_t *pte;
 
@@ -590,9 +593,13 @@ static int vmap_pages_pte_range(pmd_t *p
 			break;
 		}
 
-		set_pte_at(&init_mm, addr, pte, mk_pte(page, prot));
-		(*nr)++;
-	} while (pte++, addr += PAGE_SIZE, addr != end);
+		pfn = page_to_pfn(page);
+
+		/* A PMD boundary may split a chunk; never map past its end. */
+		chunk_end = addr + ((ALIGN(pfn + 1, chunk_pages) - pfn) << PAGE_SHIFT);
+		size = vmap_set_ptes(pte, addr, min(end, chunk_end), pfn, prot, shift);
+		nr_pages = PFN_DOWN(size);
+	} while (pte += nr_pages, *nr += nr_pages, addr += size, addr != end);
 
 	lazy_mmu_mode_disable();
 	*mask |= PGTBL_PTE_MODIFIED;
@@ -602,60 +609,88 @@ static int vmap_pages_pte_range(pmd_t *p
 
 static int vmap_pages_pmd_range(pud_t *pud, unsigned long addr,
 		unsigned long end, pgprot_t prot, struct page **pages, int *nr,
-		pgtbl_mod_mask *mask)
+		pgtbl_mod_mask *mask, unsigned int shift)
 {
 	pmd_t *pmd;
 	unsigned long next;
+	int err;
 
 	pmd = pmd_alloc_track(&init_mm, pud, addr, mask);
 	if (!pmd)
 		return -ENOMEM;
 	do {
 		next = pmd_addr_end(addr, end);
-		if (vmap_pages_pte_range(pmd, addr, next, prot, pages, nr, mask))
-			return -ENOMEM;
+
+		if (shift >= PMD_SHIFT) {
+			struct page *page = pages[*nr];
+			phys_addr_t phys_addr;
+
+			if (WARN_ON(!page))
+				return -ENOMEM;
+			if (WARN_ON(!pfn_valid(page_to_pfn(page))))
+				return -EINVAL;
+
+			phys_addr = page_to_phys(page);
+
+			if (vmap_try_huge_pmd(pmd, addr, next, phys_addr, prot, shift)) {
+				*mask |= PGTBL_PMD_MODIFIED;
+				*nr += 1U << (PMD_SHIFT - PAGE_SHIFT);
+				continue;
+			}
+		}
+		err = vmap_pages_pte_range(pmd, addr, next, prot, pages, nr, mask, shift);
+		if (err)
+			return err;
 	} while (pmd++, addr = next, addr != end);
 	return 0;
 }
 
 static int vmap_pages_pud_range(p4d_t *p4d, unsigned long addr,
 		unsigned long end, pgprot_t prot, struct page **pages, int *nr,
-		pgtbl_mod_mask *mask)
+		pgtbl_mod_mask *mask, unsigned int shift)
 {
 	pud_t *pud;
 	unsigned long next;
+	int err;
 
 	pud = pud_alloc_track(&init_mm, p4d, addr, mask);
 	if (!pud)
 		return -ENOMEM;
 	do {
 		next = pud_addr_end(addr, end);
-		if (vmap_pages_pmd_range(pud, addr, next, prot, pages, nr, mask))
-			return -ENOMEM;
+		err = vmap_pages_pmd_range(pud, addr, next, prot, pages, nr, mask, shift);
+		if (err)
+			return err;
 	} while (pud++, addr = next, addr != end);
 	return 0;
 }
 
 static int vmap_pages_p4d_range(pgd_t *pgd, unsigned long addr,
 		unsigned long end, pgprot_t prot, struct page **pages, int *nr,
-		pgtbl_mod_mask *mask)
+		pgtbl_mod_mask *mask, unsigned int shift)
 {
 	p4d_t *p4d;
 	unsigned long next;
+	int err;
 
 	p4d = p4d_alloc_track(&init_mm, pgd, addr, mask);
 	if (!p4d)
 		return -ENOMEM;
 	do {
 		next = p4d_addr_end(addr, end);
-		if (vmap_pages_pud_range(p4d, addr, next, prot, pages, nr, mask))
-			return -ENOMEM;
+		err = vmap_pages_pud_range(p4d, addr, next, prot, pages, nr, mask, shift);
+		if (err)
+			return err;
 	} while (p4d++, addr = next, addr != end);
 	return 0;
 }
 
-static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end,
-		pgprot_t prot, struct page **pages)
+/*
+ * It can take an array of pages which are not all contiguous, but it
+ * may have contiguous chunks, as hinted by @shift.
+ */
+static int vmap_pages_range_noflush_walk(unsigned long addr, unsigned long end,
+		pgprot_t prot, struct page **pages, unsigned int shift)
 {
 	unsigned long start = addr;
 	pgd_t *pgd;
@@ -670,7 +705,7 @@ static int vmap_small_pages_range_noflus
 		next = pgd_addr_end(addr, end);
 		if (pgd_bad(*pgd))
 			mask |= PGTBL_PGD_MODIFIED;
-		err = vmap_pages_p4d_range(pgd, addr, next, prot, pages, &nr, &mask);
+		err = vmap_pages_p4d_range(pgd, addr, next, prot, pages, &nr, &mask, shift);
 		if (err)
 			break;
 	} while (pgd++, addr = next, addr != end);
@@ -693,28 +728,13 @@ static int vmap_small_pages_range_noflus
 int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,
 		pgprot_t prot, struct page **pages, unsigned int page_shift)
 {
-	unsigned int i, nr = (end - addr) >> PAGE_SHIFT;
-
 	if (WARN_ON_ONCE(page_shift < PAGE_SHIFT))
 		return -EINVAL;
 
-	if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) ||
-			page_shift == PAGE_SHIFT)
-		return vmap_small_pages_range_noflush(addr, end, prot, pages);
-
-	for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) {
-		int err;
-
-		err = vmap_range_noflush(addr, addr + (1UL << page_shift),
-					page_to_phys(pages[i]), prot,
-					page_shift);
-		if (err)
-			return err;
+	if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC))
+		page_shift = PAGE_SHIFT;
 
-		addr += 1UL << page_shift;
-	}
-
-	return 0;
+	return vmap_pages_range_noflush_walk(addr, end, prot, pages, page_shift);
 }
 
 int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
_

Patches currently in -mm which might be from baohua@kernel.org are

arm64-vmalloc-allow-arch_vmap_pte_range_map_size-to-batch-multiple-cont_pte.patch
mm-vmalloc-extend-page-table-walk-to-support-larger-page_shift-sizes-and-eliminate-page-table-rewalk.patch
mm-vmalloc-map-contiguous-pages-in-batches-for-vmap-if-possible.patch
mm-vmalloc-align-vm_area-so-vmap-can-batch-mappings.patch